MAX7301AAI-T Maxim Integrated, MAX7301AAI-T Datasheet - Page 9

• Manufacturer Part Number: MAX7301AAI-T
• Description: Interface - I/O Expanders 2.5-5.5V 20/28 Port I/O Expander
• Manufacturer: Maxim Integrated
• Series: MAX7301r

Specifications of MAX7301AAI-T

• Maximum Operating Frequency: 26 MHz
• Operating Supply Voltage: 2.5 V to 5.5 V
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SSOP-28
• Output Current: 4.5 mA, 18 mA

The MAX7301 uses an external resistor, R
internal biasing. Use a resistor value of 39kΩ.
The MAX7301 operates down to 2V supply voltage
(although the sourcing and sinking currents are not
guaranteed), providing that the MAX7301 is powered
up initially to at least 2.5V to trigger the device’s internal
reset, and also that the serial interface is constrained to
10Mbps.
The MAX7301’s SPI interface is guaranteed to operate
at 26Mbps on a 2.5V supply, and on a 5V supply typi-
cally operates at 50Mbps. This means that transmission
line issues should be considered when the interface
connections are longer than 100mm, particularly with
higher supply voltages. Ringing manifests itself as
communication issues, often intermittent, typically due
to double clocking due to ringing at the SCLK input. Fit
a 1kΩ to 10kΩ parallel termination resistor to either
GND or V+ at the DIN, SCLK, and CS input to damp
Figure 3. Daisy-Chain Arrangement for Controlling Multiple MAX7301s
Figure 4. Transmission of a16-Bit Write to the MAX7301
DOUT
SCLK
DIN
CS
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
MICROCONTROLLER
D15
= 0
SERIA-CLOCK OUTPUT
SERIAL-DATA OUTPUT
Applications Information
SERIAL-DATA INPUT
SERIAL CS OUTPUT
_______________________________________________________________________________________
D14
SPI Routing Considerations
D13
Low-Voltage Operation
External Component R
D12
CS
DIN
SCLK
D11
MAX7301
D10
ISET
, to set
DOUT
D9
ISET
D8
CS
SCLK
DIN
ringing for moderately long interface runs. Use line-
impedance matching terminations when making con-
nections between boards.
For the TQFN version, connect the underside exposed
pad to GND. Ensure that all the MAX7301 GND connec-
tions are used. A ground plane is not necessary, but
may be useful to reduce supply impedance if the
MAX7301 outputs are to be heavily loaded. Keep the
track length from the ISET pin to the R
short as possible, and take the GND end of the resistor
either to the ground plane or directly to the ground pins.
The MAX7301 operates with power-supply voltages of
2.5V to 5.5V. Bypass the power supply to GND with a
0.047µF capacitor as close to the device as possible.
Add a 1µF capacitor if the MAX7301 is far away from
the board’s input bulk decoupling capacitor.
TRANSISTOR COUNT: 30,316
PROCESS: CMOS
D7
.
28-Port I/O Expander
MAX7301
D6
DOUT
D5
PC Board Layout Considerations
Power-Supply Considerations
D4
D3
CS
SCLK
DIN
Chip Information
MAX7301
D2
D1
DOUT
ISET
D0
resistor as
D15 = 0
9